421A is a clear yellow immersion tin solution designed to coat copper traces and solder deposits with a thick layer of tin. The deposited tin is readily solderable and extends the working life of circuits by protecting them from corrosion. The pure tin deposit provides excellent corrosion resistance, and is free of co‑deposited organics. 421A ensures good solderability for solder deposits by cleaning them and by making their surfaces bright and active. Features & Benefits No dilution required High tin concentration Rinsable residues Good adhesion